JP4619519B2 - Optical cross connect - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber communication system, and more particularly to an optical cross-connect structure using a micro electromechanical system (MEMS) tilted mirror array.
[0002]
[Prior art]
In fiber optic communication systems, signal routing is necessary to direct the optical signal carrying data to the intended location. Existing routing techniques suffer from optical power loss due to inefficient optical signal coupling between the input and output fibers. This increases the dependence on the optical power source (eg, pump laser) used to compensate for power loss by injecting optical power into the optical system. The need for an optical power source increases the overall cost of the optical system.
[0003]
Another essential requirement for signal routing is that signals received from one of multiple input fibers or ports can be directed to one of multiple output fibers or ports independent of the frequency of the optical signal. It is. Known optical signal routers are frequency dependent and therefore have an impact on routing multiple signals, each having a different wavelength, to the output port based on the frequency of the signal. For example, in US patent application Ser. No. 09 / 414,622 (filed Oct. 8, 1999), multiple wavelengths that are adjacent in frequency are not spatially selected output fibers, but spatially adjacent output fibers. Routed.
[0004]
[Problems to be solved by the invention]
Accordingly, the optical connect system preferably has reduced power loss and a flexible frequency routing function.
[0005]
[Means for Solving the Problems]
An improvement over previously known optical cross-connects can be realized by providing an optical cross-connect that uses an array of tilted micro-electromechanical system (MEMS) mirrors to direct optical signals from the input optical fiber to the output optical fiber. The optical cross-connect of the present invention has a lens array that receives optical signals from a plurality of input fibers. The lens array is composed of a plurality of lens elements, and each lens element directs an optical signal to the MEMS mirror array. That is, it collects light. The MEMS mirror array has a plurality of mirror elements, and each element is tilted around one or a plurality of rotation axes by applying a control signal to a desired mirror element. Thus, the optical signal can be directed to various output fibers along various paths.
[0006]
In one embodiment of the present invention, the input and output lens arrays are used together with the input and output MEMS mirror arrays. The input lens directs the input optical signal to the input MEMS array, and the input MEMS array reflects each signal in a direction related to the tilt direction of each mirror. The reflected signal is received by the output MEMS mirror row, and further reflected toward the output lens row to be coupled to the output fiber.
[0007]
In another embodiment of the present invention, the input and output lens arrays are formed on a common substrate, the reflective surface is disposed between them, and the input and output MEMS mirror arrays are first. Is formed on a second common substrate disposed at a position opposite to the substrate. The reflective surface receives the optical signals reflected from the input MEMS string and directs them to the output MEMS string.
[0008]
In yet another embodiment of the present invention, an optical element having transmission characteristics is disposed at a location that is in optical communication with the first MEMS mirror and the second MEMS mirror. The optical element directs the optical signal between the first and second mirror arrays by transmitting or reflecting the optical signal, and directs the optical signal between the first optical fiber array and the second optical fiber array. Selectively forward.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
A large-scale optical cross-connect used in an optical system can be constituted by an array of two-axis tilt mirrors realized by using micro electro mechanical system (MEMS) technology. A plurality of input optical paths are connected to a plurality of output optical paths using an optical cross connect. The general requirement for an optical cross-connect is that any input can be connected to any output. An example of the mirror array 10 is shown in FIG. This mirror row 10 has a plurality of tilting mirrors 12 mounted on a spring 14 and controlled by electrodes (not shown). Each tilting mirror 12 has a size of 100-500 μm and is shaped like a square, a circle, or an ellipse, and rotates around the XY axis with a tilt angle determined by the voltage applied to the electrodes. That is, it tilts. Details of the operation of the mirror array 10 are disclosed in US patent application Ser. No. 09 / 415,178 (filing date: Oct. 8, 1999). A general technique for constructing an optical cross-connect using a plurality of mirror arrays 10 is disclosed in US patent application Ser. No. 09 / 410,586 (filing date: October 1, 1999).
[0010]
In accordance with the present invention, optical power loss is achieved with a compact size (ie, minimal space between cross-connect components) in various optical cross-connect configurations by using one or more MEMS tilt mirror rows with lens rows. Can be realized that minimizes A cross-connect 100 according to the present invention is shown in FIG. The cross connect 100 receives an optical signal 108 through a plurality of input optical fiber arrays 112 formed as a conventionally known array. For ease of explanation, the input optical fiber array 112 is a one-dimensional array having four input optical fiber arrays 112a, an input optical fiber array 112b, an input optical fiber array 112c, and an input optical fiber array 112d. As shown. In this specification, the optical fiber array 112 and other optical fiber arrays are two-dimensional N × N arrays.
[0011]
The input optical fiber array 112 sends an optical signal 108 to the input lens array 114 that functions as a collimating lens. The input lens array 114 is positioned relative to the input optical fiber array 112 such that each lens is in optical communication with an optical fiber capable of generating a pencil beam 116 from the optical signal 108. The beam 116a is generated from the signal carried by the input optical fiber array 112a, and the beam 116d is generated from the signal carried by the input optical fiber array 112d. The same applies hereinafter.
[0012]
The first MEMS tilting mirror row 118, also referred to as an input row, is arranged in alignment with the input lens row 114, so that the tilting mirror 12 receives the beam 116. The mirror element is tilted in the manner disclosed in US patent application Ser. No. 09 / 415,178 to reflect the beam 116 to a second or output MEMS mirror array 122. The MEMS row 122 is arranged at a position that is optically connected to the MEMS row 118. Depending on the tilt angle of each mirror element in the MEMS array 118, the reflected signal is selectively directed to a particular mirror element in the MEMS array 122. To illustrate this principle, beam 116a generates reflected beam 120a and reflected beam 120a ′, and beam 116d is shown to reflect reflected beam 120d and reflected beam 120d ′. These beams are received by the mirror elements in the MEMS array 122 and directed as beams 124 to the output lens array 126. The output fiber array 128 receives the optical signal 129 in alignment with the output lens array 126. Thus, output lens array 126 couples beam 124 to output fiber array 128.
[0013]
The cross connect 100 maps each output fiber to the mirror in the output mirror array on a one-to-one basis. This is necessary for a single mode fiber because the numerical aperture required to align the input and output beams coaxially with the axis of the optical fiber to keep power loss low is small. The cross-connect in FIG. 2 can limit the mirror angle deviation that requires a sufficient space between the fiber array and the mirror array.
[0014]
A typical space dimension that reduces diffraction loss is 50-100 mm. The mirror row, the lens row, and the fiber row are on the same plane. That is, when the input optical fiber array 112, the input lens array 114, and the MEMS array 122 are on the same plane, the output fiber array 128, the output lens array 126, and the MEMS array 118 are on the same plane. Thus, two similar monolithic blocks can be formed. This cross-connect assembly only requires one 6-axis alignment.
[0015]
Another cross-connect 200 of the present invention is shown in FIG. Similar to the cross-connect 100 of FIG. 2, the cross-connect 200 has an input lens array 214 and an output lens array 226 through optical signals passing through the input optical fiber array 212 and the output fiber array 228, respectively. Let The input mirror array 218 and the output mirror array 222 are separated from the input lens array 214 and the output lens array 226 so that an optical signal can be directed between the input fiber array and the output fiber array. . Unlike the cross-connect 100, the device of FIG. 3 has MEMS mirror rows and lens rows arranged on opposite sides of the cross-connect network, which facilitates manufacturing. In particular, the mirror array is monolithically integrated on the first common substrate, and the lens array and the fiber array are monolithically integrated on the second common substrate. In order to perform signal routing between the MEMS mirror rows, the input lens row 214 and the output lens row 226 are formed on a common substrate so as to be spaced apart from each other, and as a result, the reflective element 230 is disposed therebetween. The reflective element 230 is arranged to communicate optical signals between the MEMS row 218 and the MEMS row 222 with a reflective coating material (eg, gold) formed on a separate flat mirror or lens substrate. When the lens array is arranged, the reflected beam 220 is only required to have one 6-axis alignment with a mirror array on the same plane.
[0016]
FIG. 4 shows a modification of FIG. The main difference from FIG. 3 is that the reflective element 230 is removed. As shown in the figure, the MEMS row 318 and the MEMS row 322 are inclined with respect to the substrate surface including the input lens row 314 and the output lens row 326, and as a result, the optical signal is transmitted between the mirror row and the mirror row. Direct exchange. In this embodiment, the maximum distance between each fiber row (eg, input optical fiber row 312) and the mirror row (eg, MEMS row 318) facing each other is small. This is an important design consideration, especially when the exact orientation of the fiber array is weak. The mirror elements in the mirror array can be used not only to adjust switch connections (eg, routing function), but also to compensate for imperfections in the fiber array.
[0017]
FIG. 5 shows another cross-connect 400 that employs an offset mirror 430 for the MEMS mirror row 420. In this embodiment, one fiber array 410, one lens array 416, and one MEMS mirror array 420 are used in a cross-connect configuration where they are folded. One fiber train functions as a combined input / output train. Input signal 412 is applied to lens array 416 by optical fiber 414 to form an image on MEMS mirror array 420a. Thereafter, this beam is reflected by the mirror 430, further reflected back by the MEMS mirror row 420 b, and output to the output fiber 422 through the lens row 416. There is no distinction between input ports and output ports in this configuration. Thus, without using one port, this cross-connect with a 32 × 32 mirror row can be used as a 1 × 1023 switch, or a 3411 × 2 switch row, or a 512 × 512 optical cross-connect. I can do it. Other variations exist. For example, other combinations of cross-connect elements (eg, two 1 × 128 switches, 64 2 × 2 switches, one 256 × 256 switch can be used with a 32 × 32 mirror array. ).
[Brief description of the drawings]
FIG. 1 is a plan view illustrating an example of a MEMS mirror array used with the present invention.
FIG. 2 is a diagram illustrating an optical cross-connect according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating another embodiment of the optical cross connect in FIG. 2;
FIG. 4 is a diagram illustrating still another embodiment of the optical cross-connect of FIG.
FIG. 5 depicts a “folded” optical cross-connect according to yet another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Mirror row | line | column 12 Inclined mirror 14 Spring 100,200,300 Cross connect 108,208,308 Optical signal 112,212,312 Input optical fiber row | line 114,214,314 Input lens row | line | column 116,216,316 Beam 118,218 , 318 MEMS array 120, 220 Reflected beam 122, 222, 322 MEMS array 124, 224, 324 Beam 126, 226, 326 Output lens array 128, 228, 328 Output fiber array 129, 229, 329 Optical signal 230 Reflective element 400 Cross-connect 410 Fiber array 412 Input signal 414 Optical fiber 416 Lens array 418 Beam 420 MEMS mirror array 430 Mirror 422 Output fiber

Claims (3)

In an optical cross-connect that directs optical signals received from a plurality of input optical fibers to a plurality of output optical fibers ,
A plurality of input lenses that receive the optical signals from the plurality of input optical fibers;
A plurality of output lenses for directing the optical signals to the plurality of output optical fibers;
A MEMS mirror array having an input mirror array and an output mirror array, each of the input mirror mirror array and the output mirror array having a plurality of mirror elements each having a rotation shaft that can be selectively tilted. The input mirror row is arranged to receive an optical signal directed by the plurality of input lenses, and the output mirror row is arranged to reflect the optical signal to the plurality of output lenses. MEMS mirror row,
A reflective element disposed at a position optically connected to the MEMS mirror array, which receives an optical signal directed by the input mirror array and reflects the received optical signal back to the output mirror array ; Consisting of
The output mirror array directs the optical signal reflected from the reflecting element toward the plurality of output optical fibers,
Wherein the plurality of input lens and the plurality of output lenses, are formed on a common substrate and spaced apart to form a space to each other,
The optical cross-connect, wherein the reflection element is disposed in the space and is on the same plane as the plurality of input lenses and the plurality of output lenses . The rotating shaft has a first rotating shaft and a second rotating shaft,
The optical cross-connect according to claim 1, wherein each of the mirror elements is tiltable with respect to the first rotation axis and the second rotation axis. The plurality of input lenses are adapted to receive optical signals from the plurality of input optical fibers and direct the received optical signals to the input mirror array;
The plurality of output lenses are adapted to receive an optical signal from the output mirror row and direct the received optical signal to the plurality of output optical fibers. Optical cross connect.

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